Spinning rotors used in open-end spinning machines, if necessary, for example in the case of wear or in order to manufacture a different type of yarn on the rotor-spinning machine, have to be able to be changed. Depending on the type of mounting, it may make the change of open-end spinning rotors more difficult or even impossible if the rotor cup and the rotor shaft are non-releasably connected to one another. Therefore, a large number of observations have already been made as to how the connection between the rotor cup and rotor shaft can be made releasable. Apart from the easy exchangeability of the rotor cup, the secure connection during operation of the spinning rotor is also paramount. It is to be noted here that the spinning rotor is operated at rotational speeds of 150,000 revolutions per minute and more. Rotor spinning machines are known that reach up to 200,000 revolutions per minute.
One possibility for a releasable connection of this type is described in European Patent Publication EP 1 156 142 B1. This is realised by means of a coupling device, which consists of a magnetic bearing arrangement for the axial locking of the rotor shaft and rotor cup and a mechanical anti-rotation lock, which prevents any relative rotational movement between the rotor shaft and rotor cup by means of an interlocking fit. A receiving sleeve is let into the rotor shaft by means of a press fit. The receiving sleeve has, one behind the other in the axial direction, a permanent magnet, a polygon socket and a cylindrical bore. The rotor cup has an axle stub or an attachment made of ferromagnetic material with an external polygon, which corresponds with the polygon socket, and a guide attachment, which corresponds with the cylindrical bore.
The cylindrical bore is to surround the guide attachment without play. A play-free connection of this type is not possible, however, because of the manufacturing tolerances always present. In order to ensure the exchangeability of the rotor cup, play between the cylindrical bore and the guide attachment will thus always be necessary. However, even with a small amount of play within the range of a few hundredths of millimeters, imbalance forces may be produced at the high rotational speeds, at which the spinning rotor rotates, which can damage the drive and/or the mounting of the spinning rotor. The imbalance is produced here by the axial offset between the rotor cup and rotor shaft.